The present invention relates to video signal processing and, more particularly, to video display of images from signals generated by more than one source.
It is a common practice to store information in a form which may be generated as electrical signals suitable for input to a television display device to produce an image based on the stored information. The information may, for example, be stored in digital form in a memory unit having the required signal processing and output capability, referred to in the art as a digital image generator. Such apparatus is normally programmed to produce signals which are used to modulate the horizontal scan lines on raster lines for the purpose of producing an image.
It is sometimes desirable to include in the displayed image, a discrete area produced by signals emanating from a source other than the digital image generator, e.g., a television camera. Video insetting techniques have become well-known in the art which select from a plurality of signals available for modulating the horizontal scan lines, those signals desired for inclusion in the displayed image at any given time as the display raster is generated. For example, see U.S. Pat. No. 3,787,619 granted to Hanns H. Wolff on Jan. 22, 1974. The inset portion of the display may constitute an image positionally unrelated to the primary image into which it is inset, but displayed therewith for convenience of viewing the two images in a single display, or the two images may be related in such a way as to form a composite, single scene. In the latter case, for example, an image representing a background may be digitally generated, while an object seen by a television camera is inset into the background to provide a display showing the object appearing in front of the background.
In any case, the inset portion of the display normally constitutes a predetermined fraction of the total area of the display, regardless of the image content of such portion, or constitutes a particular object whose image is inset on the display regardless of size. Further, the prior art is typically based on the assumption that the complete inset object is closer to the eyepoint from which the display is viewed than any portion of the image into which it is inset.
Therefore, it is a principal object of the present invention to provide a method of combining in a video display, images generated from more than one source, wherein objects produced by one image source may appear closer than some and farther away than other objects produced by the other image source.
A further object is to provide a video display system having inputs from either of two signal sources controlled by a video switch wherein the image of an object represented by the signals from one source both occludes and is partially occluded by objects represented by signals from the other source depending on the assumed position of the first object with respect to the others.
Other objects will in part be obvious and will in part appear hereinafter.